Originally Posted by wwest (Post 7496076)

I don't need to PROVE anything, both SCIENCE and PHYSICS side with me.

Think about what will happen to the refrigerant pressure in the system should you use a simple propane torch to heat any one of the heat exchangers, long after the system pressures have equalized....?

Now take an operating evaporator core that has just arrived at the lowest temperature control point (28F..?), the TXV is mostly closed, or fully closed as has now been demonstrated(***). Obviously the compressor was "just" cycled off so the high side pressure is at the highest level that the compressor is capable of "driving" it to.

Now, shut off the engine and watch, mentally watch, the temperature of the rear lid condensor rise higher and higher as it is HEATED via the rising engine and exhaust manifold HEAT. How long, how many minutes, does it take for the engine temperature to stop rising, post shutdown, and begin to cool?

"...no need to hook up guages to prove that.." Whole-heartedly agree.

***Post # 22:

http://forums.pelicanparts.com/porsche-911-technical-forum/755318-first-project-thread-88-cab-c-retrofit-cheap-2.html

Originally Posted by SilberUrS6 (Post 7496144)

According to wwest's hypothesis, it goes like this:

The compressor is doing work right up until the time is motor is shut off. This give the high side initial pressure. The additional work done to the closed system is due to waste radiant heat from the motor, heating the rear condenser further. Since the system volume is closed, adding temperature raises the pressure, according to the ideal gas law (which works well enough to illustrate) PV=nRT. Since the volume (V) is fixed, you can hold that constant. The actual amount of refrigerant (n) is also fixed. So you can hold that constant. R is the ideal gas constant. The variations due to different types of molecules in gas phase is quite small, so this won't change much no matter what kind of gas we're discussing. van der Waal's gas, ideal gas, they behave nearly the same at these kinds of pressures and temperatures. So that can be held constant as well. So, what you get, at the end of all that is that pressure is directly proportional to temperature (T). If the temperature of the condenser goes up, then the pressure will also rise proportionally, and linearly with temp.

Ahhh, but here is where the complication comes in. The high side pressure and the low side pressure will eventually come to equilibrium, and thus the high side pressure should NOT be the initial point from which calculations are made. It is claimed that somehow the high side stays isolated from the low side after this shut-down period, and that high side pressures continue to rise due to PV=nRT. This is the unproven and unfounded claim that wwest continues to make. He knows that he can never put gauges on and test it, because actual experimentation will show exactly what Griff claims - on shutdown, the high-side and low side slowly equalize. Why? Because they are not isolated like wwest claims. *EVERYTHING* he claims hinges on the assumption of high/low side isolation. Since the AC professionals say it doesn't happen, I'll take their professional opinion over wwest's fantasy any day.

Originally Posted by techman1 (Post 7496284)

So wwest claims you can walk up to a car that was run the prior day, hook up a set of manifold gauges, and the pressure on the high side will still be as high as the prior day?
The high side is isolated?

Originally Posted by wwest (Post 7496305)

Okay, test conditions/configuation...inconclusive fior Texans.

88 Carrera, rear lid condensor cooling fans removed, front condensor fan put back to operational status and confirmed to be operational. Digital temperature probes inserted into the rear lid condensor vanes, one at the center and the other close to the compressor high side condensor inlet. Pressure guages hooked up.

57.7F OAT. Cabin closed up, MAX cooling, lowest blower speed. Ran the engine at 2000 RPM until the compressor began cycling, indicating that the evaporator was now fully cold soaked.

Dropped the engine to idle and waited for the compressor to cycle on again and then checked /recorded readings. Both temperature probes stabilized at 120F, guages at 20 PSI and 150 PSI.

Compressor cycled off and then I immediately shut down the engine. Within a minute the high side pressure went from 150 PSI to 225 PSI and in less than 2 minutes to 250 PSI., and then began to fall fairly rapidly, down to 75 PSI both. No change on the low side for ~2 minutes at which time it began to slowly climb. Meantime the temperature probes slowly rose to 155F within about 5 minutes, and did not recede until I opened the engine lid at about 10 minutes.

Yes, OAT at only 57.7F so not exactly a valid test in comparison to 110F in TX, and/or post a HARD engine run, but most certainly proves my point.

Originally Posted by wwest (Post 7496305)

Dropped the engine to idle and waited for the compressor to cycle on again and then checked /recorded readings. Both temperature probes stabilized at 120F, guages at 20 PSI and 150 PSI.

Compressor cycled off and then I immediately shut down the engine. Within a minute the high side pressure went from 150 PSI to 225 PSI and in less than 2 minutes to 250 PSI., and then began to fall fairly rapidly, down to 75 PSI both. No change on the low side for ~2 minutes at which time it began to slowly climb. Meantime the temperature probes slowly rose to 155F within about 5 minutes, and did not recede until I opened the engine lid at about 10 minutes.

Yes, OAT at only 57.7F so not exactly a valid test in comparison to 110F in TX, and/or post a HARD engine run, but most certainly proves my point.

Originally Posted by brads911sc (Post 7496353)

It doesnt matter where you are located.

Either the pressure would rise... or not.

Get out your guages and do a 30 second test. What is the harm. Its your theory. You could have PROVED ypour theory 1000 times in the amouty of time you rant on here trying to convince people with no data or proof.

Originally Posted by brads911sc (Post 7496355)

post a video.

Originally Posted by wwest (Post 7496357)

Can you not read? Or maybe cannot comprehend what you read. You "quote" my test procedure yet you appear to have NOT read it....

Originally Posted by wwest (Post 7496362)

Would it suffice to have my corporate attorney certify my findings?

There is already a proving video...post # 22

http://forums.pelicanparts.com/porsche-911-technical-forum/755318-first-project-thread-88-cab-c-retrofit-cheap-2.html

Originally Posted by brads911sc (Post 7496365)

there is no video doing what you state. You run your own test, your own video. Come on. Whats the harm...

Originally Posted by wwest (Post 7496367)

i think i'll go with the attorney...

Originally Posted by wwest (Post 7496367)

I think I'll go with the attorney...

Originally Posted by Mr Project (Post 7496392)

If there's one thing we can agree on, it's that attorneys are 100% accurate in all technical matters and would never over- or under-state a position in order to serve a certain purpose.

The only possible improvement I can think of would be if you could get a politician to review your results and certify them here. That would be truly unimpeachable proof, much better than a video, which can be so easily digitally altered by any garden-variety 73-year-old.

Originally Posted by brads911sc (Post 7496355)

post a video. put the naysayers out of business. whats the harm. Have only been asked a few 100 times in 30 threads.

Originally Posted by SilberUrS6 (Post 7496481)

Wait. He says it climbs to 250psi? OK, so what? 250psi is within the operating range of the components. Well within. He was BSing 800psi yesterday. Even if the OAT is 200 degrees, the system is not going to get to 800psi. At *any* point.

Since the "T" in the PV=nRT equation is absolute (in Kelvin), a jump in OAT from, say 70 degrees (294K) to 100 degrees (310K) is a little more than 5% increase in temperature. So the pressure would, in an ideal gas, jump a little more than 5% in pressure in a closed system. If the temperature of the condenser jumped up to, oh, 200 degrees F (366K), the pressure increase would be slightly more than 20% from 70 degrees F. So, for the example where someone shuts off with a high side at 150psi, that means a 20% increase would leave us with a high side max at 180psi.

Even if, running R134a, and seeing high side pressures of 250 steady-state, the 20% increase would be to 300psi. That's pretty high for steady-state operation, but as a peak pressure is well within the limits of the system.

Originally Posted by SilberUrS6 (Post 7496481)

Wait. He says it climbs to 250psi? OK, so what? 250psi is within the operating range of the components. Well within. He was BSing 800psi yesterday. Even if the OAT is 200 degrees, the system is not going to get to 800psi. At *any* point.

You have DATA to verify/confirm that OPINION...?

OAT is NOT the point. At 57.7F the rear lid condensor was operating at 120F, then went to 155F due to loss of cooling and rising (both meanings) engine HEAT. What might the condensor temperature rise to with a 100F OT starting point. On top of all that my low OAT was also keeping the engine a LOT cooler than might be at 90-100 OAT.

Since the "T" in the PV=nRT equation is absolute (in Kelvin), a jump in OAT from, say 70 degrees (294K) to 100 degrees (310K) is a little more than 5% increase in temperature. So the pressure would, in an ideal gas, jump a little more than 5% in pressure in a closed system. If the temperature of the condenser jumped up to, oh, 200 degrees F (366K), the pressure increase would be slightly more than 20% from 70 degrees F. So, for the example where someone shuts off with a high side at 150psi, that means a 20% increase would leave us with a high side max at 180psi.

Even if, running R134a, and seeing high side pressures of 250 steady-state, the 20% increase would be to 300psi. That's pretty high for steady-state operation, but as a peak pressure is well within the limits of the system.

Originally Posted by brads911sc (Post 7496355)

post a video. put the naysayers out of business. whats the harm. Have only been asked a few 100 times in 30 threads.

Originally Posted by wwest (Post 7496573)

IMO NOTHING will satisfy the 2 primary NAYSAYERS (+Kuehl, of course) other than having the WORSE of them actually witness the testing.

Planning a trip to MT this summer, SilberUrS6, you up to being a witness?